Air conditioning system



NOV 21, l939 H.- w. HEISTERKAMP AIR CONDITIONING SYSTEM Filed Sept. 25,1937 2 Sheets-Sheet 1 INVENTOR. HE/Psf/w' M #wsrf/WAMP ATTORNEY Nov. 21,1939.

H. W. HEISTERKAMP AIR CONDITINING SYSTEM Filed Sept. 25, 1937 2.Sheets-Sheet 2 ATTORNEY5 Patentedl Nov. 21, 1939 i 2,180,437 L AIRCONDITIONING SYSTEM Herbert W., Heisterkamp, Cleveland, Ohio, asf signorto The Bryant Heater Company, Cleve land, Ohio, a corporation of OhioApplication september z5, 1937, serial No. 165,710

Z Claims.

This invention relates to improvements in air conditioning systems, andparticularly that class of air conditioning systems in which bothdehumidifying and cooling are desired and in which the air isdehumidiiied by causing it to come into contact with an adsorptivematerial of which silica gel is an example.

An object of the invention is the provision of a system in which theamount of cooling surface or the amount of cooling water is reduced ascompared with what has been required heretofore in air conditioningsystems of this class.

Other objects and features of novelty will appear as I proceed with thedescription of those embodiments of the invention which, for thepurposes of the present application, I have illusdamp air, after beingbrought into intimate con` tact with silica gel or the like, is dryA butmuch warmer, the extent oi the warming being of the order of .774 F. pergrain 'of moisture removedv from each pound of dry air.- This is thetemperature rise occasioned by the transformation of the latent heatrepresented by one grain of water vapor plus the so-called heat -oi'adsorption which is of the order of .0343 B. t. u. per grain of watervapor adsorbed. The heat of adsorption may be considered as representingor arising from it from the air.

It is characteristic of silica gel and other similar adsorptivematerials that the cooler and drier the air which is delivered intocontact with-the adsorptive material, the greater the percentage of theair bornel moisture that it removes. Hence the silica gel is made moreeil'ectiveand the opf erationof the entire air conditioning system moreeconomical if the air previous to being brought into contact with thesilica gel is cooled to below its dew point and. partially dried, andthis can be done by bringing it into contact with coils l through whichcold water is flowing. Well water at a temperature in thefneigbborhoodof 55 the work done upon the water vapor inA separating to F. is wellsuited to this purpose, and its use in this manner is well known in theu In the accompanying drawings and in the description to follow I havedisclosed a system util,- izing silica gel apparatus as a dehumidifying5 means in such manner that the amount of equip ment is reduced and thecost correspondingly lessened.

In the drawings III represents the compartment to be air conditioned,that is to be main- 10 tained at a predetermined temperature andhumidity level. For example, let us assume that the desired condition isdry bulb temperature and 65.8 wet bulb temperature, with 72 grains ofmoisture per pound of dry air. The compartment 15 III constitutesa partof a recirculating system including air conductors II, I2 and I3 and afan or blower I4 by means of which the circulation is maintained. I5 isa fresh air conductor which may be considered as connecting with therecir- '20 culating line at the junction of conductors II and -.I2. Byway oi' example it may be assumed that the outdoor fresh air is at a drybulb temperature of with a moisture content of 120 grains per pound ofdry air. The fresh air is 25 caused to pass through a precooler I6supplied with water from a pipe I'I leading from a source A of supply,such as a well. Let it be assumed that; this water is at a temperatureof 56.

The precocler I6 may be of well known design 30.

and construction, and a typical one'when supplied with 56 water willcool the -95 air to adry bulb temperature of 61 and a wet bulbtemperature of 59.7, at which condition the air will contain 75 grainsof moisture per, pound, the 35 diii'erence between this 'and theoriginal 120 grains, that is 45 grains, having been precipitated bycondensation on the cold surfaces of the pre- 'cooler. g j

Conductor I5 conveys this cool and partially 40 dry air to silica geldehumidiiler I8, from which it willv issue at a theoretical temperatureof 102, containing 22 grains of moisture per pound of dry air. It is tobe understood that the water removing eiiiciency here assumed is merelytypi- 45 cal and is subject t0 variation in accordance with theproportioning and mechanical design of the dehumidifier. v Y

Referring to Fig. l, air is withdrawn from compartment III throughconductor II by the 50 suction eiect of fan ill. Conductor I'I connectswith conductor I2 in which there is placed a c ooler I9 similar inconstruction to precooler I6, and likewise supplied with'56 water fromsupply Pipe IIand branch pipe III.

The relation between the quantity of air withdrawn through conduit lland that drawn through conduit I5 depends upon the sources of heat andmoisture within the conditioned compartment, but a typical relationwould be 10,000 C. F. M. (cubic feet per minute) through conduit II and5,000 C. F. M. through conduit I5.

The dry air leaving the dehumidier I6 passes through a cooler 2| whichis supplied through pipe 23 with the water which has previously beenused in precooler I6 and cooler I9. A discharge pipe 26 from cooler I 9and a discharge pipe 25 from precooler I6 are connected to pipe 23.Drain pipe '26 carries all of the water away to a suitable place ofdisposal. The purpose of cooler 2| is to cool the air discharged by thedehumidiiier, which is warm for the reasons that have been previouslyset forth, down to a temperature approaching or below the temperature tobe maintained within the compartment i6.

With the cooling water entering coolers I6 and I9 at a temperature of 56F. it would be common practice to have it leave these coolers at 66, andwe will assume that condition here. Then the water entering cooler 2lthrough pipe 23 would be at a temperature of 66 F., and the airdischarged from cooler 2l into the recirculating line may in a typicalcase be at a temperature of 73. If then, for example, the temperature tobe maintained Within conditioned compartment I was 80, the

' temperature in conduit I2 would be that resulting from the mixing of10,000 C. F.` M. of 80 air and 5,000 C. F. M. of 73 air, producing15,000 C. F. M.

`of 77.67 air.

A thermostat 27, located in conduit IIof the recirculating line,responds Ito the changes in temperature of air in conduit II, andaccordingly graduates or modulates the opening of a valve 28 throughwhich water is supplied to cooler I9.

Thermostatic controls of this character are Well conductor 3l connectingthe thermostat with the valve operator, and ar conductor 32 running fromthe valve operator back to linewire 33.

During periods when the humidity in compartment I 0 is above the desiredlevel fresh air is drawn through dehumidifier I6 to be fed into therecirculating line. In practice the dehumidifier is provided with aself-contained fan which draws the fresh air through the dense bed ofsilica gel that is contained in the dehumidier and discharges it intoconduit I5 on the delivery side of the dehumidifier. During periods whenthe humidity in compartment I6 stands at or below the desired level thefan in the dehumidifier is of course idle and the passage of air throughconduit I5 is therefore blocked. In order to feed fresh air to therecirculating line at such times an air by-pass or shunt line isprovided around the dehumidier so that a iiow of fresh air into therecirculating line may1 be induced by the action of fan It. Such aby-pass conductor is shown herein at 36. It is desirable that thisby-pass be closed when the dehumidifier is operating. Consequently Iprovide a' valve 35, shown closed in the drawings. The valve is providedwith an electric control which when energized holds the valve closed.When the control is deenergized gravity acts to open the valve.

An electric conductor 36 extends from line wire 30 to the dehumidier.Another conductor 31 extends from the dehumidiiier to a humidostat 38located in conductor Il of the recirculating line, and a returnconductor 39 connects the humidostat with line wire 33. A pair of shuntconductors i0 and 4I connect conductors 36 and 3l respectively with theterminals of a solenoid 42 constituting the operating means for closingvalve 35.

Prior to the present invention it has been the conventional practice toconnect by-pass 34 to conduit I2 on the inlet side of the cooler I9. Inaccordance with the present invention however this connection is madeupon the outlet side oi' the cooler. 'I'his simple change results in asurprising economy which I will now demonstrate and explain.

Let it be assumed that the heat load upon compartment I0 is such thatair must leave cooler I9 and be delivered into campartment I0 at atemperature of 65. When the dehumidifier I 8 is in operation, and inaccordance with the assumptions previously made, air enters coolerI I9at a temperature of 77.67, and at a temperature rise of the water ingoing through cooler I9 of from 56 to 66. The temperature relation isthus expressed as Air in 77.67 l Air out 65 Water out 66 Water in 56which corresponds to a logarithmic mean temperature difrerence of 10.33.The heat to be removed from the air amounts to 10 8.3f2.."241'02 gallonsper minute since there are 8.34 pounds of water in a gallon. This waterquantity together with the mean temperature difference is a factor indetermining the number of rows of tubes required in cooler I9,

counting in the direction of air iiow, and thecondition for whichcalculations have just been made is the maximum condition which sets thecooler depth.

Now assume that dehumidier I8 'is not in operation. By-pasf'I conduit 3dis then open. There will now be 10,000 C. F. M. of air passing throughcooler i6, uniting with the 5,000 C. F. M. of by-passed air to producethe 15,000 C. F. M. required for delivery to the conditionedcompartment. It is required that the mixture of 10,000 C. F. M. cooledfrom 80 in cooler I9, with the 5,000 C. F. M. of by-passed air at atemperature of 6l", produce 15,000 C. F. M. at 65. The temperature towhich the 10,000 C. F. M. must 'be cooled is calculated as follows:

'Ihe amount of heat to be removed in cooler I9 is 10,000.018(80-67)=2340 B. t. u. per minute The temperature relation betweenwater and air passing through cooler I9 is represented partially asfollows:

.11n1n. 80 Airaut er? Water in 56 15,ooo .o1a` '13.6'165 :2340 B. t. u.per minute The temperature relation between water and air passingthrough cooler I9 is represented as follows: Air1n '13.67 A1r mt 65Waterin 56- It will be seen by inspection therefore that in theheretofore conventional system .the difference between ingoing water andoutgoing air is 9 as compared with 11 in a system arranged according tothe presentinvention. It will be apparent immediately to those skilledin the art that during those times when air is being bypassed around thedehumidiiler the water required by cooler I9 will be less in a systemdesigned according to this invention than in a' system designedaccording to conventional practice, on account of the greaterconcentration of heat in the entering side and the greater airto-watertemperature on the leaving side. The result is a reduced waterconsumption during a great deal of the operating time of the system,leading to lowered operating costs.

In Fig. 2 there is shown a variation of the system shown in Fig. 1, thecooler I9 having been removed from conduit I2 and a cooler I9' havingbeen introduced into conduit Il. All other features of the system andall of the reference characters remain the same as in Fig. 1.

The air quantities and temperatures remaining the same as in Fig. l, itwill be seen that since cooler I9 needs now, to be large enough only topass 10,000 C. F. M. of air, its frontal size will become less than thatof cooler I9 in conduit I2, for in the case of cooler I9 it wasoccasionally necessary for the frontal size to be sufiicient to pass15,000 C..F. M. of air, thatis during times when dehumidier I8 was inoperation. Moving the cooier from conduit I2 to conduit II does notmaterially aiect the mean .temperature diierence, and thereforethecooling water required is shown by -the following calculations:

The heat to be removed from the air amounts to 10,000X.018 (80-60.97):3425.4 B. t. u. per minutel andthe water required amounts to Thetemperature'relation is expressed by Airin 80 Air out 60.97 Water out 66Water in 56 =4l.07 gallons per minute which corresponds to a meantemperature differenceof`8.75. These are the conditions which set thecooler depth.

When dehumidifier I8 is not in operation the 5,000 C. F. M. dischargedfrom precooler. I6 into conduit I2 by means of conduit 34 is at atemperature of 61. Since it is required that the 15,000 C. F. M. of airentering compartment l be at 65, it is necessary that the 10,000 C. F.M. passing through cooler I9' be cooled to 67 in order to produce amixture temperature ofl 65 when it is mixed with the 5,000 C. F. M. of61 air.

10,000 .018(8067)=2340 B. t. u. per minute The temperature relation ofwater and air passing through cooler I9 is represented as follows: Airin80 Air out 67 Water in 56 Inspection and comparison will now show thatduring those periods of operation in which air is being by-passed aroundthe dehumidifier, the benecial result of delivering the by-passed airinto the system on the outlet side of the last cooler Ais preserved,whether it be cooler I9 in conduit I2 or cooler I9' in conduit vII, andfurther when cooler I9 in conduitull is used there is the additionaladvantage that its necessary frontal size becomes reduced.

Having thus described my invention, I claim: 1. In anair conditioningsystem, an air recirculating line including a compartment in which theair is to be conditioned, an air cooling means in said line, means forintroducing dehumidied air into said line on the intake side of saidcooling means, and means for introducing fresh cooled outdoor air intosaid line on the outlet side of said cooling means.

2. In an airconditioning system, an air re circulating line including acompartment in which the air is to be conditioned, a dehumidier of theadsorption type, an air cooler on the inlet side of said dehumidifier,an air cooler in *said recirculating'line, means for conducting airHERBERT W. HEISTERKILMIP.

- ond cooler.

The heat to be removed from the air amounts

